1. Field of the Invention
The present invention relates to an optical pickup apparatus, and particularly, to an optical pickup apparatus for an optical disc using a semiconductor laser element.
2. Description of the Background Art
Conventionally, an optical pickup apparatus employing a semiconductor laser element has been used as an apparatus for recording and reproducing a signal on an optical disc. With the optical pickup apparatus, laser diffusion light emitted from the semiconductor laser element is converted into parallel light by a collimator lens and collected on the optical disc by an objective lens.
However, there has been a problem with the conventional optical pickup apparatus that an astigmatic difference of the semiconductor laser element causes astigmatism in a light spot on the optical disc, whereby an excellent light spot cannot be attained.
Accordingly, a method has been proposed, wherein a collimator lens is arranged to be tilted by a prescribed angle with respect to the direction perpendicular to an optical axis, so that the astigmatism caused by the astigmatic difference of the semiconductor laser element is compensated for by astigmatism obtained by the tilt arrangement of the collimator lens (for example, see Japanese Patent Laying-Open No. 8-147747).
However, there has been a problem with the conventional method that the astigmatism that varies depending on apparatuses cannot precisely be corrected for because of the fixed tilt angle of the collimator lens, and that an excellent light spot cannot be attained.